THIS RESEARCH FOLLOWS ON FROM MY EARLIER WORK ON HYPOXIC DEFENSE MECHANISMS IN A VERTEBRATE ANAEROBE, THE WESTERN PAINTED TURTLE. THIS SPECIES DEMONSTRATES AN ABILITY TO COORDINATELY REDUCE MEMBRANE PUMP AND CHANNEL ACTIVITY, THEREBY STABILIZING THE CELL MEMBRANE DURING ANOXIA-INDUCED METABOLIC SUPPRESSION (TERMED ~CHANNEL ARREST~). AT THE NVPF, I HAVE EXAMINED THE RESPONSE OF CA2+-FLUX TO ANOXIA IN ISOLATED TURTLE HEPATOCYTES USING THE ION-SELECTIVE CA2+ VIBRATING ELECTRODE. EARLY RESULTS DEMONSTRATE THAT CA2+ FLUX IN THESE CELLS IS PREDICTABLY RESPONSIVE TO ACTIVATORS AND INHIBITORS OF PROTEIN KINASE-C, IS REVERSIBLY DOWN-REGULATED DURING ANOXIA AND RE-OXYGENATION, AND DEMONSTRATES AN OXYGEN DEPENDENCY, WITHOUT THE METABOLIC ROLE OF OXYGEN (DOWN-REGULATION DOES NOT OCCUR IF ANOXIA IS MIMICKED BY INHIBITING MITOCHONDRIAL OX-PHOS). FUTURE STUDIES ARE DESIGNED TO TEST THE RELATIONSHIP BETWEEN OXYGEN, SECOND MESSENGER SYSTEMS AND THE CONTROL OF CA2+ FLUX.